While in its broadest aspects the present invention provides a process for surface modifying a variety of polymeric support surfaces, it is primarily directed toward new and improved membranes in which a support membrane is modified by irreversibly adsorbing onto essentially all the surfaces of the support membrane a suitable polymeric modifying material.
Membrane modifying processes disclosed heretofore involve depositing a layer of coating material on the membrane by solvent evaporation. In these processes, a solution of the modifying material is applied to the membrane, excess solvent removed from the membrane and the membrane dried to remove the remaining solvent. In some cases a surfactant is added to aid in obtaining a more uniform distribution of modifying material. This results in a modifier on the membrane whose thickness is determined by the amount of solution retained by the membrane and the concentration of the modifier solution. The coating can be stabilized by crosslinking the modifying material during drying. Inherent limitations in these methods are formulating the modifying material to obtain a sufficiently thin, uniform distribution of polymer on the membrane and often having the modifying material concentrated at one surface of the membrane.